Study of Defects and their Impact on Transport and Thermoelectric Properties in Monolayer Silicene: an Ab Initio Simulation
Monalisa Ghosh, Subhechcha Banerjee, Arnab Mukhopadhyay, Sahid Iqbal Mallick, Lopamudra Banerjee
Indian Institute of Engineering Science and Technology, Shibpur, India
Here we present atomistic simulation study on the impact of defects on electronic transport and thermal properties of monolayer silicene. We have introduced four different type of defects in monolayer silicene sheet and these are single vacancy defects, stone-wales defect, edge roughness and ring missing defect. We have used Density functional theory (DFT) – Non equilibrium Green’s function (NEGF) approach to study transport in pristine as well as in defective sheets. We have simulated the electron transmission and phonon transmission of the perfect and various defective sheets. We have simulated energy resolved transmission and I-V characteristics of pristine and defective sheets. Our simulation shows significant decrease in carrier conductance in the presence of defects as compared to pristine silicene sheet. Our investigation also shows a gradual decrease in current as the number of vacancy increases. We have computed electron conductance, peltier coefficient, Seebeck coefficient, heat transport coefficient for electron and phonon, thermal conductance and thermoelectric figure of merit ZT. Our computation presents a significant increase in ZT in presence of defects. ZT values for edge roughness, single vacancy defect, stone-wales defect are almost two times greater than pristine silicene sheet. Our simulation also shows a notable decrease in thermal conductance of silicene sheets for vacancy defects and stone-wales defect, edge roughness as compared to that for the perfect sheet. We have compared ZT of various defective sheets with pristine silicene sheet and this shows that edge rough silicene is better thermoelectric material as compared to perfect silicene.
Silicene; defects; thermoelectric property; transmission spectra; density functional theory (dft)